The advent of virtualization technologies for commodity hardware has provided benefits for many customers with diverse needs, allowing various computing resources to be efficiently and securely shared between multiple customers. For example, virtualization environments such as those provided by VMWare, XEN, Hyper-V and User-Mode Linux may allow one or more physical computing machines to be shared among multiple users by providing each user with one or more virtual machines hosted by one of the physical computing machines. Each such virtual machine may be a software simulation acting as a distinct logical computing system that provides users with the illusion that they are the sole operators and administrators of a given hardware computing resource, while also providing application isolation and security among the various virtual machines. Furthermore, some virtualization technologies are capable of providing virtual resources that span one or more physical resources, such as a single virtual machine with multiple virtual processors that actually spans multiple distinct physical computing systems, etc.